To increase the aerodynamic stability in turbomachines such as jet engines or stationary gas turbines, it is known to expand the so-called pumping limit of compressors. For this purpose, an airflow is usually blown into the main flow in the blade tip area of a front rotating blade row. The airflow, as shown in WO 2009/143820 A2, may be an external airflow or, as shown in patent EP 1 382 855 B1, a partial flow which was bled from the main flow in the area of a rear compressor stage. In general, complex external tubing is necessary to obtain and supply the airflow to be blown in.
To increase the thermal stability of a turbomachine, it is known to provide an active clearance control (ACC), in particular on turbines, to set a radial clearance of the rotating blade tips in relation to the turbine housing. Such a clearance control is shown for example in U.S. Pat. No. 6,454,529 B1. This known clearance control has a plurality of plate-like annular segments which have an external tubing for supplying a cooling airflow to the turbine housing bled on the compressor side. The problems with this clearance control are, however, the great complexity of the device and assembly as well as a significant weight increase of the turbomachine due to the tubing.